---
layout: docs
page_title: Distributed Tracing
description: >-
  Distributed tracing is a way to track and correlate requests across microservices.
---

# Distributed Tracing

Distributed tracing is a way to track and correlate requests across microservices. Distributed tracing must first
be implemented in each application, it cannot be added by Consul. Once implemented in your applications, adding
distributed tracing to Consul will add the sidecar proxies as spans in the request path.

## Application Changes

Consul alone cannot implement distributed tracing for your applications. Each application must propagate the required
headers. Typically this is done using a tracing library such as:

- https://github.com/opentracing/opentracing-go
- https://github.com/DataDog/dd-trace-go
- https://github.com/openzipkin/zipkin-go

## Configuration

Once your applications have been instrumented with a tracing library, you are ready to configure Consul to add sidecar
proxy spans to the trace. Your eventual config will look something like:

<CodeTabs tabs={[ "HCL", "Kubernetes YAML", "JSON" ]}>

```hcl
Kind = "proxy-defaults"
Name = "global"
Config {
  protocol           = "http"
  envoy_tracing_json = <<EOF
{
  "http":{
    "name":"envoy.tracers.zipkin",
    "typedConfig":{
      "@type":"type.googleapis.com/envoy.config.trace.v3.ZipkinConfig",
      "collector_cluster":"collector_cluster_name",
      "collector_endpoint_version":"HTTP_JSON",
      "collector_endpoint":"/api/v2/spans",
      "shared_span_context":false
    }
  }
}
EOF

  envoy_extra_static_clusters_json = <<EOF
{
  "connect_timeout":"3.000s",
  "dns_lookup_family":"V4_ONLY",
  "lb_policy":"ROUND_ROBIN",
  "load_assignment":{
    "cluster_name":"collector_cluster_name",
    "endpoints":[
      {
        "lb_endpoints":[
          {
            "endpoint":{
              "address":{
                "socket_address":{
                  "address":"collector-url",
                  "port_value":9411,
                  "protocol":"TCP"
                }
              }
            }
          }
        ]
      }
    ]
  },
  "name":"collector_cluster_name",
  "type":"STRICT_DNS"
}
EOF
}

```

```yaml
apiVersion: consul.hashicorp.com/v1alpha1
kind: ProxyDefaults
metadata:
  name: global
spec:
  config:
    protocol: http
    envoy_tracing_json: |
      {
        "http":{
          "name":"envoy.tracers.zipkin",
          "typedConfig":{
            "@type":"type.googleapis.com/envoy.config.trace.v3.ZipkinConfig",
            "collector_cluster":"collector_cluster_name",
            "collector_endpoint_version":"HTTP_JSON",
            "collector_endpoint":"/api/v2/spans",
            "shared_span_context":false
          }
        }
      }
    envoy_extra_static_clusters_json: |
      {
        "connect_timeout":"3.000s",
        "dns_lookup_family":"V4_ONLY",
        "lb_policy":"ROUND_ROBIN",
        "load_assignment":{
          "cluster_name":"collector_cluster_name",
          "endpoints":[
            {
              "lb_endpoints":[
                {
                  "endpoint":{
                    "address":{
                      "socket_address":{
                        "address":"collector-url",
                        "port_value":9411,
                        "protocol":"TCP"
                      }
                    }
                  }
                }
              ]
            }
          ]
        },
        "name":"collector_cluster_name",
        "type":"STRICT_DNS"
      }
```

```json
{
  "Kind": "ProxyDefaults",
  "Name": "global",
  "Config": {
    "protocol": "http",
    "envoy_tracing_json": "{\"http\":{\"name\":\"envoy.tracers.zipkin\",\"typedConfig\":{\"@type\":\"type.googleapis.com/envoy.config.trace.v3.ZipkinConfig\",\"collector_cluster\":\"collector_cluster_name\",\"collector_endpoint_version\":\"HTTP_JSON\",\"collector_endpoint\":\"/api/v2/spans\",\"shared_span_context\":false}}}",
    "envoy_extra_static_clusters_json": "{\"connect_timeout\":\"3.000s\",\"dns_lookup_family\":\"V4_ONLY\",\"lb_policy\":\"ROUND_ROBIN\",\"load_assignment\":{\"cluster_name\":\"collector_cluster_name\",\"endpoints\":[{\"lb_endpoints\":[{\"endpoint\":{\"address\":{\"socket_address\":{\"address\":\"collector-url\",\"port_value\":9411,\"protocol\":\"TCP\"}}}}]}]},\"name\":\"collector_cluster_name\",\"type\":\"STRICT_DNS\"}"
  }
}
```

</CodeTabs>

-> **NOTE:** This example uses a [proxy defaults](/docs/connect/config-entries/proxy-defaults) config entry which will apply to all proxies
but you can also apply this config in the
[proxy service registration](/docs/connect/registration/service-registration#proxy-parameters) (not supported on Kubernetes).

Within the config there are two keys you need to customize:

1. [`envoy_tracing_json`](/docs/connect/proxies/envoy#envoy_tracing_json): Sets the tracing configuration for your specific tracing type.
   See the [Envoy tracers documentation](https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/trace/trace) for your
   specific collector's configuration. This configuration will reference the cluster name defined in `envoy_extra_static_clusters_json`.
1. [`envoy_extra_static_clusters_json`](/docs/connect/proxies/envoy#envoy_extra_static_clusters_json): Defines the address
   of your tracing collector where Envoy will send its spans. In this example the URL was `collector-url:9411`.

## Applying the configuration

This configuration only applies when proxies are _restarted_ since it changes the _bootstrap_ config for Envoy
which can only be applied on startup. This means you must restart all your proxies for changes to this
config to take effect.

-> **Note:** On Kubernetes this is a matter of restarting your deployments, e.g. `kubectl rollout restart deploy/deploy-name`.

## Considerations

1. Distributed tracing is only supported for HTTP and gRPC services. You must specify the protocol either globally
   via a proxy defaults config entry:

    <CodeTabs tabs={[ "HCL", "Kubernetes YAML", "JSON" ]}>

   ```hcl
   Kind      = "proxy-defaults"
   Name      = "global"
   Config {
     protocol = "http"
   }
   ```

   ```yaml
   apiVersion: consul.hashicorp.com/v1alpha1
   kind: ProxyDefaults
   metadata:
     name: global
   spec:
     config:
       protocol: http
   ```

   ```json
   {
     "Kind": "proxy-defaults",
     "Name": "global",
     "Config": {
       "protocol": "http"
     }
   }
   ```

    </CodeTabs>

   Or via a service defaults config entry for each service:

    <CodeTabs tabs={[ "HCL", "Kubernetes YAML", "JSON" ]}>

   ```hcl
   Kind      = "service-defaults"
   Name      = "service-name"
   Protocol  = "http"
   ```

   ```yaml
   apiVersion: consul.hashicorp.com/v1alpha1
   kind: ProxyDefaults
   metadata:
     name: service-name
   spec:
     protocol: http
   ```

   ```json
   {
     "Kind": "service-defaults",
     "Name": "service-name",
     "Protocol": "http"
   }
   ```

    </CodeTabs>

1. Requests through [Ingress Gateways](/docs/connect/gateways/ingress-gateway) will not be traced unless the header
   `x-client-trace-id: 1` is set (see [hashicorp/consul#6645](https://github.com/hashicorp/consul/issues/6645)).

1. Consul does not currently support interoperation with [OpenTelemetry](https://opentelemetry.io/) libraries due to
   Envoy not yet having support.

1. Tracing is only supported with Envoy proxies, not the built-in proxy.

1. When configuring the Zipkin tracer in `envoy_tracing_json`, set [`trace_id_128bit`](https://www.envoyproxy.io/docs/envoy/v1.21.0/api-v3/config/trace/v3/zipkin.proto#envoy-v3-api-field-config-trace-v3-zipkinconfig-trace-id-128bit) to  `true` if your application is configured to generate 128-bit trace IDs. For example:

   <CodeBlockConfig highlight="10">

   ```json
   {
     "http": {
       "name": "envoy.tracers.zipkin",
       "typedConfig": {
         "@type": "type.googleapis.com/envoy.config.trace.v3.ZipkinConfig",
         "collector_cluster": "zipkin",
         "collector_endpoint_version": "HTTP_JSON",
         "collector_endpoint": "/api/v2/spans",
         "shared_span_context": false,
         "trace_id_128bit": true
       }
     }
   }
   ```

   </CodeBlockConfig>
